(1) Field of the Invention
This invention relates to an electroconductive coating material. More particularly, the invention relates to an electroconductive coating material which is used to impart electroconductivity to surfaces of nonconducting materials or to impart anti-static property to goods which should be prevented from electrostatic charges.
(2) Description of Prior Art
As electroconductive coating materials used for imparting electroconductivity to the surfaces of nonelectroconductors, there are hitherto proposed several kinds of coating materials which contain powder or fiber material of electroconductors such as metals or carbon black. Such art is employed widely to a considerable extent in industrial practice, however, there remains various kinds of problems to be solved.
For example, even though a method to blend an electroconductive powder is easily carried out, it is necessary to mix the powder as much as 20 to 40% into a coating material. Accordingly, this method raises the production cost of coating material.
As compared with the use of powder material, the necessary quantity of fibrous material is smaller to obtain a certain effect. However, because the fibrous materials are inorganic substances likewise in the case of powder mixing method, the coating film is liable to be peeled off to reduce the effect, at the same time, the peeled broken pieces will make surroundings dirt. In addition, the dispersibility of blended substance in coating material is not good because the specific gravity of blended substance is large, which makes the formation of uniform coating difficult.
Furthermore, when numerous fibrous materials are protruded from the surface of coating in the form of needles, excellent anti-static effect can be expected by the effect of lightning rod. However, the needle-like tips are liable to be broken by external force such as contact and friction and the effect of lightning rod is rapidly lowered.
Meanwhile, the method to apply a solution of an anti-static agent solution is inexpensive and relatively easy to be carried out, however, it is quite difficult to reduce a surface specific resistance to a level lower than 10.sup.8 .OMEGA..multidot.cm. What is worse, it is not desirable in practice because the attained anti-static property is not good enough and is lost within a period from 1 month to 1 year.